1. Field of the Invention
The invention relates to a method for removing gaseous, volatile and/or liquid impurities from waste gases from industrial processing plants.
2. Description of the Prior Art
A device for carrying out such a method is disclosed in German Offenlegungsschrift No. 24 45 315 which utilizes, as an absorbent, compost from the incomplete decomposition of organic wastes.
Such devices, known as so-called "bio-filters", have in the past been utilized for filtering the outgoing or exhaust air from composting plants or composting partially drained domestic sludge, that is, for removing the organic impurities.
It has also been suggested to use bio-filters of this type for the removal of impurities from waste gases from industrial sewage treatment plants and industrial processing plants, particularly of the chemical industry. An analysis of waste gases from sewage treatment plants of the chemical industry, particularly of the pharmaceutical industry, has shown that such waste gases contain organic as well as inorganic gaseous, volatile and/or liquid impurities in the form of hydrogen sulfide, ammonia, ammonium compounds, thiols or aliphatics, cycloaliphatics or aromatic hydrocarbons. The impurities found most often in the waste gases are hydrogen sulfide, ammonia, ammonium compounds and thiols. The same impurities are contained in waste gases from the manufacture of penicillins and cephalosporins and from the purification of the sewage generated by this manufacture.
A long series of tests has now shown that the above-mentioned bio-filters are not suitable for the removal of these waste gases if the waste gases are to a substantial degree halogenated. It is possible that, in the biomass which is used as an absorbent, there develops a growth of microbes which effectively remove halogenated waste gas components as a result of natural selection after a period of months. However, such a development is merely accidental and cannot be used on a technical scale.
Therefore, it is the primary object of the invention to further develop the known method for the removal of impurities from waste gases in such a way that halogenated hydrocarbons are effectively removed and that the method can be utilized on a large industrial scale. This object is to be achieved without requiring long start-up periods for the microbiological processes in the biomass which is used as the absorbent.